This disclosure is generally directed to the machining of metallic components. In some specific embodiments, the disclosure is related to the electromachining of components formed from advanced structural metals and alloys.
Advanced metallic materials play an increasingly important role in modern manufacturing industries like aircraft, automobile, and tool- and die-making industries. The materials usually exhibit greatly-improved thermal, chemical, and mechanical properties, as compared to conventional materials. Specific properties that are enhanced include strength, heat resistance, wear resistance, and corrosion resistance. Even modest improvements can result in considerable economic benefits to manufacturing industries through improved product performance and product design.
While the advanced materials exhibit many desirable attributes, they are sometimes very difficult to process. As an example, traditional machining and casting processes for specialized materials such as titanium alloys are often inadequate, and require the removal of large amounts of stock, when forming plates, bars, and the like. Moreover, the operations often need to be supplemented by additional processes, such as multiple finishing operations. Also, the chemical and physical properties of titanium and its alloys can make drilling operations challenging, often resulting in an undesirably large heated affected zone (HAZ). For these reasons, the overall processing cost can be much higher, as compared to materials like steel.
A number of techniques have been developed to process advanced materials like titanium and nickel superalloys. Electrical discharge machining (or EDM) is a machining method primarily used for hard metals, or those that would be impossible to machine with traditional techniques. The technique is carried out with rapidly-recurring electrical arcing discharges between an electrode (the cutting tool) and the work-piece, in the presence of an energetic electric field. The EDM cutting tool is guided along the desired path very close to the work-piece, but it does not touch the work-piece. This technique is sometimes referred to as “electroerosion”. Other electromachining techniques are also known in the art, including electrochemical machining (ECM), electrochemical grinding (ECG); and electrochemical discharge machining (ECDM), all described in U.S. Pat. No. 7,741,576 (A. Trimmer et al).
While current electromachining processes are acceptable in many situations, additional design and performance requirements for various high-performance alloys have prompted the search for considerable advances in the processes. As an example, certain components formed from titanium and its alloys can still be very difficult to machine, due to lower thermal conductivity, and the inability keep the machining region free from process debris. As described below, the machining debris can imperil the electroerosion process, and can result in damage to both the machining equipment and the work-piece. Moreover, there is still a need to improve the material removal rate (MRR) for machining high-performance alloys in an industrial setting, since excessive machining times and the need for many other processing steps can decrease the economic viability of the overall process. Thus, improved electroerosion processes that address some of these challenges would be welcome in the art.